[c-nsp] deactivate line with too many packet drops?

[Gert Doering]

Hi,

is there a way (e.g. using BFD, or some other magic smoke) to deactivate
a line that has more than "x" percent packet loss?


Background: yesterday evening one of our backbone lines (Gbit ethernet, 
transported over a supplier's MPLS backbone) had severe hickups.  About 
50% packet loss, but no garbled packet (packets just didn't arrive, no 
input errors), and of course the interface status was "up/up" all the time,
not a single link flap (so anything that's tied to input errors or link
flaps, like IP interface dampening, isn't going to work).


Needless to say that iBGP was *very* unhappy with this (TCP sessions got
stuck due to high packet loss, keepalives didn't get through, BGP sessions
getting reset, high CPU in "BGP I/O" on a large number of core routers, 
etc).  EIGRP/OSPF weren't overly happy either, neighbours forming and
getting lost in regular intervals.

Setting the interface to "passive" in EIGRP and OSPFv3 immediately cured
all problems (iBGP sessions being routed around the line, BGP restabilizing,
etc.) - as was to be expected.

The thing that annoys me is that I had to do this manually - it would be
so much better if the router had a way to figure out "oh, this line is
seriously fubar, *do not use it*".


I think this is something that could nicely fit into BFD, but as far as
I can see, it's not there.

Any other ideas how to auto-disable such a link?

(GigE on both sides, 7603/12.2(18)SXE2 on one end, 7301/12.2(18)S9 on
the other end, 7301 could be swapped against another 7603 if that helps)

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de